The Village Bike

Greta Gerwig could have found a much easier vehicle than “The Village Bike.”

But no, the blond star of “Frances Ha” and other indie films picked a doozy of a stage debut — one that requires her to watch porn with one hand down her panties, get it on graphically with a co-star and, through it all, speak in an English accent.

But Gerwig, who stepped in after Maggie Gyllenhaal withdrew from the project, pulls it all off with her usual unaffected ease and wide-eyed, lovable spirit. She lends such natural charm to Penelope Skinner’s complicated heroine, Becky, that you can’t stop caring about her.

And Becky needs all the caring she can get. Her new pregnancy has made her prim, do-gooder husband, John (Jason Butler Harner), lose all interest in sex — except for sneaking in an X-rated film, he’d rather do the dishes.

This baffles Oliver (Scott Shepherd), the strapping neighbor who’s just sold Becky a used bike: “Why bother with porn when you’ve got the real thing right in front of you?”

You can see why Becky would start an affair with Oliver, who’s also married but ready and willing to play while his wife’s away. Together they indulge in fantasies they’d never share with their spouses — at one point Becky, an English teacher, turns up in a schoolgirl uniform out of a Britney Spears video.

This all sounds like the premise of a terrible sex farce, or maybe a Judd Apatow movie — the title is, after all, British slang for a slut.

Happily, the playwright is smarter than that, casting a judgment-free eye on a woman’s desires. And the cast, sensitively directed by Sam Gold, gives nuanced performances, especially when the tone darkens after Oliver’s wife (Lucy Owen) returns and the local plumber, Mike (Max Baker), is drawn into the action.

“The Village Bike” isn’t a perfect play — John is cartoonishly dense, and there’s way too much contrived talk about their cottage’s plumbing — but Becky’s travails stay with you. You can’t help but hope she’ll be happy, and that her husband will rise to the challenge of making her so.